Datensatz

Zusammenfassung

Broken-symmetry density functional theory was used to study the catalytic center of manganese catalase in the superoxidized Mn^III/Mn^IV state. Heisenberg exchange coupling constants, ⁵⁵Mn and ¹⁴N hyperfine coupling constants (hfcs) and nuclear quadrupole splittings, as well as the electronic g tensors were evaluated for different model systems of the active site after complete geometry optimizations in the high-spin and broken-symmetry states. A comparison of the experimental data with the spectroscopic parameters computed for the models with unprotonated and protonated μ-oxo bridges shows best agreement between theory and experiment for a Mn₂(μ-O)₂(μ-OAc) core. The calculated Mn–Mn distances and ⁵⁵Mn hfcs clearly support a dimanganese cluster with unprotonated μ-oxo bridges in the superoxidized state. Furthermore, it is shown that an interchange of the Mn^III and Mn^IV oxidation states in this trapped valence system leads to specific changes in the molecular and electronic structure of the manganese clusters.